1. Field
Some example embodiments may relate to balancing apparatuses for balancing cells included in batteries and/or battery modules.
2. Description of Related Art
A battery is formed by connecting stacks in parallel, each stack having a plurality of single cells connected serially, in order to achieve a high voltage and large capacity. Ideally, the cells have identical characteristics, but deviations (a difference in capacity, impedance, and the like) occur due to technical or economical limitations in manufacturing the cells. The deviations increase as a temperature difference between cells and the number of times the cells are charged or discharged increases. Since a cell having small capacity gets over-charged or over-discharged due to deviations between cells during charging or discharging, the life span of the cell may be reduced. In addition, the life span of a battery formed of a combination of stacks, each stack being formed of cells connected in series, is determined by the cell having the shortest life span, so the life span of the battery may be also correspondingly reduced. Therefore, to adjust voltages of each of the cells to be the same value, namely, balancing, of the cells is necessary.
As an example of balancing between cells, there is a scheme for transferring energy between a module and a cell by using a multiple wound transformer. When energy is transferred from a cell of a high voltage to a cell of a low voltage according to this scheme, the energy is transferred from the high voltage cell to the module via a balancing circuit, and the energy is then transferred from the module to the low voltage cell via the balancing circuit. That is, when energy is transferred from the high voltage cell to the low voltage cell, the energy passes through the balancing circuit twice, thereby causing unnecessary energy consumption. In addition, since a transformer has windings on a single core and a single bobbin equal to the number of cells, a transformer design becomes more difficult and a size of a balancing circuit becomes larger, as the number of cells gets larger.